Mechanism◆Article
The new MP4 tab analyzes animated SVGs, renders frames, and uses ffmpeg.wasm to compile them into a video file entirely within the browser.
A new feature detects animations in SVGs and compiles them into MP4 videos using ffmpeg.wasm directly in the browser. ✦ AI generated
Simon Willison · Simon Willison's Weblog · 2026-08-16 · original ↗
The MP4 tab is new today - it examines the SVG to see if it contains any animations, attempts to guess how long the looped video should be, then renders a whole bunch of frames of the animation and loads 30+MB of ffmpeg.wasm so it can compile those frames into an MP4 video using the full power of FFMPEG compiled to WebAssembly and running in the browser.
Read full article ↗excerpt · fair-use quotation
- ·Examines SVGs for embedded animations
- ·Guesses optimal loop duration
- ·Renders animation frames as individual images
- ·Compiles frames into MP4 entirely client-side
- ·Loads 30+MB ffmpeg.wasm module
- ·Full FFMPEG power via WebAssembly
- ·Zero server-side processing required
- ·Browser-native video compilation pipeline
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In practice · 2
The tool has evolved into the ideal solution for sharing Markdown transcripts that include SVG documents.Simon Willison · Simon Willison's Weblog · conf 85%Converting animated SVGs to MP4 enables easy sharing on platforms that lack native support for SVG animations.Simon Willison · Simon Willison's Weblog · conf 85%